Field of the Invention
The invention relates to the field of methods for determining a distance between two spatial points by way of recording and evaluating pictures that include a reference object. The invention moreover relates to computer programs, which include software for the determining of the distance, which is described above, and to electronic apparatuses.
Description of Related Art
Such a method, for example, is known from EP 2 511 650 A1, which describes a method for detecting a size of an installation space for a door or a window. Thereby, a calibration element is arranged at an edge of the installation space, and a picture encompassing the calibration element and the installation space is recorded. A size ratio of the installation space to the calibration element is determined from an evaluation of the picture. This size ratio and the dimensions of the calibration element then permit a determining of the effective size, i.e. the real dimensions of the installation space.
A disadvantage of the described method from the state of the art lies in the fact that this method can determine a distance only between points that are encompassed by the same picture. Thereby, apart from the measurement points, the calibration element (also indicated as a reference object) must yet also be simultaneously encompassed by the picture. This necessitates the measurement points as well as the reference object being simultaneously visible, seen from a viewing point of a recording device taking the picture.
A further disadvantage of the described method from the state of the art lies in the fact that the reference object as well as two measurement points must be spatially arranged in the same plane. If the reference object and the two measurement points do not lie in the same plane, then the determining of the distance between the two measurements points becomes inaccurate. The method from the state of the art thus does not carry out a depth correction, and thus a determining of a distance of measurement points lying outside a plane encompassing the reference object is subject to error and is inaccurate on account of this. However, an arrangement of the reference object in a plane encompassing the two measurement points is difficult or not possible at all in many situations.
An arrangement of the reference object in a plane which encompasses both measurement points is particularly difficult or even impossible, in particular on measuring three-dimensional objects. This is the case, for example, if a line connecting the two measurement points runs through the three-dimensional object and not on its surface. In particular, a determining of the distance between the two measurement points at best is cumbersome or not even possible, if at least one of the two measurement points is covered, thus is arranged roughly behind an undercut, a projecting edge or a collar.
Moreover, the described method from the state of the art has the disadvantage that all measurement points must lie in the same plane, in which more the reference object must also lie, for an accurate measurement of distances between more than two measurement points. Thus, it is not possible to measure a distance between three measurement points without errors, if the reference object does not also lie in this plane. As the case may be, a separate picture must be taken and a separate distance measurement carried out, for each individual measurement point pair, with the method from the state of the art. This is cumbersome, for instance when determining distances between several points of three-dimensional objects. This is particularly disadvantageous if the measurement points are only difficulty accessible, such as with inner structures of three-dimensional objects or with assembled parts.
A determining of a distance between a first measurement point and a second measurement point and which is different from zero is also not possible if the second measurement point is not visible, but instead a plane running through the second measurement point with further measurement points lying in this plane is visible.
This, for example, is disadvantageous if characteristic dimensions of a lock cylinder of a door lock are to be determined. The characteristic dimensions of a lock cylinder are distances in each case between an outer side of armatures of a door lock and a position of a forend screw in the lock cylinder. Moreover, a distance indicated as a backset can also be of interest. The backset is the distance between the face side of the door and a middle axis of the lock cylinder or a middle axis of an opening in the armatures of the door lock, said opening receiving the lock cylinder. The characteristic dimensions and, as the case may be, also the backset are important, for example, on equipping doors that already have door locks, but do not yet have a lock cylinder, for the first time. A determining of the characteristics dimensions of the lock cylinder and, as the case may be, of the backset are also of interest with repairs and/or the replacement of lock cylinders.
The face side of the door is thereby indicated as a side of the door, through which a door latch is moved on closing the door lock. The forend screw is a screw which runs from the face side of the door, into the door and through the lock cylinder and by way of this fastens the lock cylinder in the door. Thus the position where the forend screw is located inside the lock cylinder is not visible from the outside, but is important for determining the characteristic dimensions of the lock cylinder. The head of the forend screw in the face side of the door, or the opening in the face side of the door that is envisaged for this however is visible, but does not lie in the same plane as the openings for the lock cylinder in the fittings. A determining of these distances is only possible with a large effort and/or with a large inaccuracy with the described method from the state of the art.